This invention relates generally to a fusing apparatus employed in an electrostatographic printing machine, and more particularly concerns an apparatus for applying release material to a heated fuser member employed therein.
In the process of electrostatographic printing, a latent image is recorded on a surface and rendered visible with particles. These particles may be transferred to a sheet of support material, in image configuration, or remain on the surface. In either case, the particles are permanently affixed to the sheet of support material or surface. In this manner, a copy of an original document is formed. Electrostatographic printing includes both electrophotographic and electrographic printing. Electrophotographic printing employs a light image of the original document to dissipate a charged photoconductive surface. This results in a latent image of the original document being recorded on the photoconductive surface. Electrographic printing does not employ a photoconductive member or a light image to create a latent image of the original document. Generally, both of the foregoing processes employ heat settable particles to develop the latent image. These heat settable particles are permanently affixed to the copy sheet by the application of heat thereto.
Many different types of systems have been developed for applying heat to the particles on the copy sheet. For example, the sheet of support material may pass between a pair of opposed rollers. In a system of this type, one of the rollers is heated while the other roller may be unheated. The outer surface of the heated roller frequently is covered with a polytetrafluoroethylene coating, commonly known as Teflon, to which a release agent, such as silicone oil is applied. An alternate system employs a bare metal heated roller having a low molecular weight polyethylene applied thereto. In this latter technique, the release materials, i.e., polyethylene, is generally a solid at room temperature. However, when the bare metal roll is heated, the release agent liquifies. It has been found that during solidification, the release agent tends to shrink. Solidification starts at the far end of the chamber storing the release material and consequently shrinks away from the fuser.
Accordingly, it is a primary object of the present invention to improve the release agent applying apparatus by constraining the release agent to solidify more closely proximate to the fuser roll.